Apologies, I wrote a long message, thinking I’d was in my DMs.

My short advice would lean toward the lowest end of the temp range.

WEAR A GOOD MASK

I’m older, grew up in a dangerous industry, and play fast and loose with a lot of rules. But this stuff will burn you in a place you cannot bandage. Protect eyesight and lungs, this is paramount in doing anything.

 

From my experience, and from what I have read, you are optimum treating anytime (50-77 degrees F) (10-25 degrees C).

When temps start approaching 0 degrees C, general opinion is the bees are clustered tighter and the OAV cannot be distributed as well on the bees.

Randy Oliver was asked this question this week. Specific question was should OAV be performed early in morning, while more bees are in the hive vs out foraging during day. Randy said his studies was the bees would contact the OA moving over frames and the hive vs direct-contact during initial dispersion of the OA. He said it was good to treat anytime, without worrying about time of the day.

I treat when I have time, not worrying about time/temp.

Best wishes.

 

Any temperature above 6 degrees C is good for OAV, however in higher temperatures bearding is a problem and when this takes place it is better to treat early in the morning when it is cooler, and bees have not started bearding. I do not believe that the temperature at the time of treatment effects the efficacy of the OAV, but there is a theory that the vapor does not get into clustered bees at temperatures below 6 degrees C, but I have seen no evidence proving this to be true.

 

The minimum temperature you can get is 3ºC .